Field of the Invention
The present invention relates to a technique for reducing image blurring or image distortion in an image pickup system including a lens device and a device body which communicate with each other.
Description of the Related Art
A technique of detecting a shake applied to an image pickup apparatus and correcting image blurring due to the shake is known. Image blurring correction by moving an image blurring correcting lens depending on the detected shake is referred to as optical image blurring correction or optical blurring control. Image blurring correction of correcting blurring for a captured image at the time of capturing a moving image by excising a part of a captured image depending on the detected shake is referred to as electronic image blurring correction or electronic blurring control.
Recently, a technique of enhancing an image blurring correction effect for large image blurring due to walking shots or the like by particularly widening an image blurring correction range on a wide side (a wide angle side) at the time of capturing a moving image is also known. By using the optical image blurring correction and the electronic image blurring correction together, it is possible to achieve a greater correction effect and to cope with larger image blurring.
On the other hand, in an interchangeable lens type camera system, a configuration in which a lens device attached to a camera body includes an optical image blurring correcting mechanism and the camera body includes an optical image blurring correcting unit or an electronic image blurring correcting unit is considered. That is, such a camera system is a system in which the lens device and the camera body are combined to perform independent blurring correction. In such a system, a technique in which the lens device and the camera body do not independently control image blurring but controls the image blurring in cooperation by communication with each other to enhance a correction effect is disclosed. Japanese Patent Laid-Open No. 2014-39131 discloses a technique in which the camera body transmits exposure time (shutter speed) information to a lens unit and a plurality detection timings of an image blurring correcting unit are determined on the basis of the shutter speed information. Japanese Patent Laid-Open No. 2015-141391 discloses a technique in which a camera body and a lens unit perform blurring correction on the basis of blurring correction rates thereof.
In an interchangeable lens type camera system, in order to cope with combinations of various interchangeable lenses and a camera body, it is necessary to perform control without recognizing individual lens specifications or camera specifications. When a communication traffic volume and a communicating frequency are great between the camera body and the lens device, there is a possibility that processing will not be completed within a prescribed time and it is thus necessary to communicate with a smaller communication traffic volume at a matched control timing.
In Japanese Patent Laid-Open No. 2014-39131, it is disclosed that the shutter speed information is transmitted in synchronization with a vertical synchronization timing and that the lens device holds a sampling table to determine a sampling timing depending on an exposure time. However, the sampling timing suitable for rolling shutter distortion correction is not uniquely determined depending on the exposure time, but may vary depending on specifications or a photographing mode of an imaging element mounted on the camera body. Accordingly, it is difficult to cope with various camera specifications.